1. Field of the Invention
This invention relates to a production process of silicon carbide short fibers, and more particularly to a production process of silicon carbide short fibers performed continuously and capable of mass producing silicon carbide short fibers in a short period of time.
2. Discussion of the Background
As for conventional production processes of silicon carbide whiskers, the following processes have been known:
Japanese Unexamined Patent Publication No. 120599/1983 discloses a production process of silicon carbide whiskers: A raw material "A" comprising a mixture of fine powder of silicate compound and carbon, and a raw material "B" comprising fine powder of carbon are prepared in a predetermined mole ratio and disposed adjacent to each other. In the raw material "A", the silicate compound and carbon are so mixed that the ratio of silicon dioxide (SiO.sub.2) to carbon (C) is set to a predetermined ratio. Then, both of the raw materials "A" and "B"are heated at temperatures of 1300.degree. to 1600.degree. C. in a non-oxidizing atmosphere to produce silicon carbide whiskers in the raw material "B".
Japanese Unexamined Patent Publication No. 172297/1983 discloses another production process of silicon carbide whiskers: A silicon source raw material mainly composed of silicon dioxide (SiO.sub.2) and furnace carbon black are heated at temperatures of 1300.degree. to 1800.degree. C. in a non-oxidizing atmosphere to produce silicon carbide whiskers.
Further, Japanese Unexamined Patent Publication No. 178413/1986 discloses a production process of silicon carbide powder comprising the steps of oxidizing a metallic silicon powder in an oxidizing gas atmosphere into silicon monoxide in the form of ultrafine particles or gas, and carbonizing the silicon monoxide in a reducing gas atmosphere containing carbon, thereby producing silicon carbide powder.
The above conventional production processes of silicon carbide whiskers have the following problems:
(a) A large amount of electricity is required because silicon carbide whiskers formation reaction is an endothermic reaction.
(b) Productivity of the conventional production processes is low because the silicon carbide whiskers are produced by the batch. Accordingly, the conventional production processes result in increasing production cost.
(c) The conventional processes require a long period of reaction time.
(d) Moldabilty of fiber reinforced metals is not good when the silicon carbide whiskers produced by the conventional production process are employed for fiber reinforced metals, because the silicon carbide whiskers have a large aspect ratio, i.e. ratio of length of whiskers to diameter thereof.
In addition, the third production process mentioned above is for producing silicon carbide powder, and it features to produce the silicon carbide powder by performing a homogeneous core formation at relatively high temperatures. Consequently., it is impossible to produce short fibers by this production process.